The present invention relates generally to apparatus and methods for mixing cementitious materials, such as mortar and grout, and more particularly relates to portable systems for mixing these materials at construction sites.
Disclosed in copending U.S. application Ser. No. 252,379 is a portable, on-site system for batch mixing cementitious construction materials, such as mortar and grout, which has proven to be a substantial improvement over prior on-site batch mixing systems. The system includes a truck-transportable batch mixing machine operative to store and batch-mix the three components of cementitious construction material-namely, cement, sand and water. The machine supports, on a frame structure, water, cement and sand storage and dispensing vessels which, via a mixing control system described in detail in the copending application, accurately deliver predetermined quantities of these three stored constituents to a bladed batch mixer portion of the machine used to subsequently mix a desired "batch" of the resulting grout, mortar or the like for construction site use.
Substantial economics of operation at job sites requiring greater numbers of batch volumes can be effected using in combination with the system a bulk cement storage facility which automatically delivers cement to the batch cement mixing proportioning hopper as disclosed in application Ser. No. 07/537,475. This not only allows the cement to be purchased in truckload lots but reduces equipment and manpower costs.
The batch mixer portion of the mixing machine illustrated in copending U.S. application Ser. No. 252,379 is provided with a generally conventional bearing and seal structure operatively associated with the drive shaft which extends through the mixer housing. In common with the shaft bearing/seal structures on other types of cementitious mixers, it has been found that this structure requires frequent greasing maintenance, and tends to rather quickly permit seal abrasion and resulting entry of the cementitious mixture into the shaft bearing. Such entry of the abrasive mixture into the shaft bearing, as is well known, leads to premature bearing failure. The intense usage of the batch mixer in the mixing apparatus of the present invention resulted in excessive down time for maintenance of the bearings.